The invention relates to a screw joint with a sealing ring, a connecting piece and a union nut for making a tube connector, the sealing ring being designed as a cutting ring with one or several cutting edges which can be inserted into a conical bore of the connecting piece starting from an end face by screwing the union nut onto the connecting piece, and the sealing ring being provided with an annular reinforcement on the nut side of its outside which forms a ring surface at its transition to the narrow ring portion.
Cutting-ring unions in which the cutting ring used is provided with several cutting edges which are arranged axially one behind the other are known, for instance, from DE 12 96 901. This patent also reveals that the cutting ring is to be provided with a reinforcement pointing radially outward on a portion of its axial length at the end of the nut side. When carrying out the assembly, the cutting ring area is squeezed into the cone of the connecting piece by actuating the screw-on nut, thereby effecting a deflection of the cutting edges towards the tube jacket and cutting into the jacket. The annular reinforcement on the nut side brings about a limitation of the range of deflection and, thus, stabilization of the cutting ring.
A screw joint with a cutting ring which is provided with a reinforcement designed as ribs and spread over the circumference is known from DE 33 41 726. The ribs point radially outward and extend axially. At their end facing the nut, they are provided with a stop face adapted to the conical bore of the nut. With their other end, they form a stop face with the end face of the connecting piece. As soon as the named stop faces reach their respective counterfaces, the torque to be applied by the fitter increases sharply, indicating the end of the assembly operation.
The assembly instructions for cutting-ring screw joints according to DIN 3859, Part 2, specify that the union has to be assembled after finger-tight screwing with 1xc2xd turns of the union nut (complete assembly). After a disassembly, however, it is no longer objectively discernible, whether these instructions have been carried out correctly. According to the assembly instructions, a visual assessment of the collar throw-up caused by the cutting edges is carried out. However, such an assessment is always subjective and depends on the experience of the fitter. The assembly operation carried out is not verifiable at the stop faces and the collar throw-up on the tube jacket. Even if overtightening was carried out, this cannot be clearly recognized by viewing the stop faces and the collar throw-up.
Therefore, the object of the invention is to indicate means by which the quality of a completed assembly operation is objectively discernible and can be demonstrated at any time by disassembly of the system.
According to the invention, the solution of this task is achieved in that the annular face resulting from the reinforcing portion of the cutting ring is provided with an inclination between 45xc2x0 and 90xc2x0, in relation to the tube axis, and that the axial length of the annular reinforcement is of such a size that, in case of complete assembly, the transfer elements arranged on the annular face transfer their negative image formation or themselves onto the end face of the connecting piece.
According to the invention, the transfer elements have spatially designed contours whose negative image formation is transferable onto the end face of the connecting piece. Similar to an embossing die, the negative image is embossed into the end face of the connecting piece by the squeezing force exerted by the fitter. This operation is assisted by the fact that the surface of the cutting ring is hardened so that, in contrast, the end face of the connecting piece has a lesser hardness, thereby facilitating the embossing operation.
In a simplified embodiment, the transfer elements are designed as corrugated elements. Such an embossed pattern can be easily made, is visually discernible without problem and, in addition, is safely palpable in bad visibility conditions.
In a further variation of the invention, the transfer elements are designed as company logos.
In a further embodiment of the invention, the transfer elements are designed as dye pigments. As a result of the buildup of the annular face of the cutting ring onto the end face of the connecting piece during the initial assembly, the assembly torque increases sharply and transfers the transfer elements onto the end face of the connecting piece. The sharp increase of the assembly torque is a signal for the fitter that assembly has been successfully completed. At the same time, when effecting disassembly, the assembly condition achieved can be objectively verified at the end face of the connecting piece since there must be corresponding embossed patterns or color codes if the initial assembly has been carried out as instructed.
In a variation of the invention, the transfer means can also be used to demonstrate overtightening of the system. In doing so, the axial length L1 of the annular reinforcement is of such a size that transfer elements arranged on the annular face transfer their negative image formation or themselves onto the end face of the connecting piece only in case of over-tightening. In this embodiment, the axial length of the annular reinforcement L1 is, therefore, designed shorter. Consequently, no contact of the ring face of the cutting ring with the end face of the connecting piece takes place in case of complete assembly and the 1xc2xd turns of the union nut to DIN, but only in case of overtightening, i.e. approximately 1xc2xe turns of the union nut. Provided assembly is correct, the shortened annular reinforcement L1 will have a relatively low stiffness, thus dampening vibration transmissions similar to the effect of metallic springs.
The invention relates to a screw joint with a sealing ring, a connecting piece and a union nut for making a tube connector, the sealing ring being designed as a cutting ring with one or several cutting edges which can be inserted into a conical bore of the connecting piece starting from an end face by screwing the union nut onto the connecting piece, and the sealing ring being provided with an annular reinforcement on the nut side of its outside which forms a ring surface at its transition to the narrow ring portion. The annular face resulting from the reinforcing portion of the cutting ring is provided with an inclination between 45xc2x0 and 90xc2x0 in relation to the tube axis and the axial length of the annular reinforcement is of such a size that, in case of complete assembly, the transfer elements arranged on the annular face transfer their negative image formation or themselves onto the end face of the connecting piece.
The transfer elements have spatially designed contours whose negative image formation is transferable onto the end face of the connecting piece. Similar to an embossing die, the negative image is embossed into the end face of the connecting piece by the squeezing force exerted by the fitter.